Chapter 8: Dreaming: Function And Meaning

Why do we have dreams and what do they mean? These questions
have for centuries been the subject of a debate that has
recently become the center of a heated controversy. In one
camp we have a number of prominent scientists who argue that
we dream for physiological reasons alone and that dreams are
essentially mental nonsense devoid of psychological meaning:
"A tale told by an idiot, full of sound and fury, signifying
nothing." The idea that dreams are nothing more than
"meaningless biology" sounds absurd and rather blasphemous to
the opposing camp, a coalition of Freudians and other dream
workers committed to the view that we dream for psychological
reasons and that dreams always contain important information
about the self or some aspects of one's life which can be
extracted by various methods of interpretation. This camp
takes its credo from the Talmudic aphorism that "an
uninterpreted dream is like an unopened letter." There is
also a third camp occupying the middle ground, that believes
both of the extreme positions on the function and meaning of
dreams to be partly right and partly wrong. Its proponents
argue that dreams may have both physiological and
psychological determinants, and therefore can be either
meaningful or meaningless, varying greatly in terms of
psychological significance.

This middle position is where I find myself most comfortable.
I agree with Sir Richard Burton that

"Truth is the shattered mirror strown in myriad bits;
while each believes his little bit the whole to own."

Perhaps, however, we may be able to put together enough of
the pieces to reflect the reality of the dream reasonably
well. Although people have argued for many centuries over
whether dreams represent the addle-minded children of an idle
brain, the heaven-sent embodiment of wisdom, or something in
between, we will confine our discussion to "scientific"
theories of dreaming at least as modern as the 20th century.
So then, let us start with Dr. Sigmund Freud.

The Interpretation Of Dreams Revisited

If we are to understand Freud's view of the dream, we need to
consider his concept of the dreamer's brain. We know today
that the nervous system contains two types of nerve cells
(excitatory and inhibitory). Both types discharge and
transmit electrochemical impulses to other neurons. Both do
this spontaneously, without any kind of outside stimuli, as
well as when they themselves receive excitatory impulses from
other cells. However, one critical difference between these
two types of neurons is that one type, called "excitatory"
transmits impulses to other neurons which causes increased
nervous activity or "excitation" in them. The other type of
neurons is called "inhibitory," because they send messages to
other neurons that cause decreased activity or "inhibition."
The human brain is constructed of an unimaginably complex
network of intricate interconnections between billions of
each type of neuron. Generally, the inhibitory neurons play a
more important role in the higher functions of the brain.

Before developing his theory of dreams, Dr. Freud had
intensively studied neurobiology. But, in his time, only the
process of excitation had been discovered; the process of
inhibition was not yet known. Based on the assumption of a
completely excitatory nervous system, Freud reasoned that
nervous, or in his terms, "psychic," energy could therefore
only be discharged by means of motor action. This meant that
once you got a notion in your head, it was doomed to run
around in there forever until you finally decided to do
something about it. Or, alternatively, until it found a way
to trick you into unconsciously expressing it in some
unintended action like the famous "Freudian slip."

This older view of the nervous system has been caricatured as
a "cat on a hot tin roof" model, "with the persistent
internal drives generating blasts of energy that keep the ego
and conscious system in frenzied movement." [1] We know today
that a nervous system of this sort, if it could exist at all,
would erupt into uncontrolled seizure activity. However,
given the state of knowledge of his time, Freud's view of the
unconscious mind as a cauldron seething with socially
unacceptable impulses and desires appears perfectly
reasonable; and likewise, from it his theory of dreaming can
readily be seen to follow.

Let us imagine what might have happened if you were somehow
able to ask the master himself why you had a particular
dream. Dr. Freud, we may speculate, might have answered
something like this:

In the first place, we may be sure that something happened
to you a day or two before the dream and that this "day
residue"--as we call it--stirred up one of the many repressed
wishes that you try to keep closeted away in your
unconscious. But, when you drifted off to sleep with no other
wish in your conscious mind than to sleep, you withdrew your
attention from the external world, setting the stage for your
day residue and associated unconscious wish to step forward,
demanding satisfaction. All this requires the cooperation of
the chief executive of your conscious mind, the ego. But
because your pair of suppliants were not, let us say,
'dressed in a socially acceptable manner,' they were at first
denied admission to your conscious mind. And that was as it
should be! It is the special function of the gate-keeper to
prevent unruly and unacceptable impulses, memories, or
thoughts from disturbing your ego's conscious mind. The gate-keeper,
which we psychoanalysts call the 'censor,' is able to
do his job with the help of a big stick we call 'repression,'
by means of which these impulses, memories, and thoughts
which conflict with personal and social standards of behavior
are banished from the conscious mind, along with the painful
emotions and memories associated with the conflict. Since the
repressed contents cannot be banished entirely, they settle
to the bottom of your unconscious mind, where they simmer and
seethe like a witches' cauldron.

But now and then, by the power of association, the events
of the preceding day, in the form of day residues, dredge up
these repressed wishes. Naturally, they seek a way to even
partial fulfillment. That is what your day residue and
repressed wish were doing, knocking on the door of the ego.
However, after the censor threw them out, the vulgar pair,
knowing nothing of manners, continued to clamor for
admission, raising such a rumpus as to threaten your precious
sleep and thereby frustrate your ego's only conscious wish.
Fortunately, you were able to continue to sleep, thanks to
your dream doing its job. As we say, 'dreams are the
guardians of sleep.' Across the border, in your unconscious
mind, a special process that we call 'dream-work' constructed
a disguise for your repressed wish, out of 'acceptable'
imagery linked to it by association. Thus transformed into a
superficially presentable image, your wish was able to get by
the censor and find expression in the your dreams.

"And that is why," Dr. Freud might well have said, "you had
that dream; and please note," he might not have been able to
resist continuing, "that your dream killed two birds with one
stone: while preserving your sleep, it also allowed the
discharge of one of your repressed instinctual impulses. That
all this was a good thing seems undeniable;" Sigmund Freud
might have concluded, "I need hardly add we regard it as
axiomatic that the nervous system obeys the 'nirvana'
principle, forever seeking the reduction of tension and the
ultimate cessation of action."

In some ways, of course, this aspect of psychoanalysis has
strong parallels with Buddhism and other Eastern doctrines.
But that brings us no closer to answering your original
question, and you might well ask: "But what did my dream
mean? Or was it just nonsense?" In that case, Freud would
have probably explained that "Every dream has some hidden
meaning; since the manifest content of the disguised dream
(the dream itself) was the result of the dream-work's
transformations of the undisguised wish (the latent content
of the dream). Therefore, in order to interpret your dream,
it should simply be necessary to reverse the process. Since
the dream disguised the latent content with images closely
associated with the original wish, we can uncover the hidden
message by reasoning backward from the image through a
process of interpretation known as "free association." If you
had dreamed, let us say, that you were locking a door, Dr.
Freud would ask you what was the first thing that comes into
your mind in connection with the work "lock?" If you said,
"key," Freud would continue, "key?" And perhaps you would
reply, "tree." This, as you can see, might go on forever,
except that Freud would probably have interrupted the process
at this point and drawn on his knowledge of dream symbolism
(key in lock...!) explaining that your dream expressed a wish
to engage in sex!

In other words, Freud believed that the function of dreaming
was to allow the discharge of repressed instinctual impulses
in such a way as to preserve sleep, and that the instigating
force causing dreams to occur was always an instinctual,
unconscious wish. Dr. Freud considered these unconscious
wishes to be predominantly sexual in nature. In "Introductory
Lectures on Psycho-Analysis," he wrote: "Though the number of
symbols is large, the number of subjects symbolized is not
large. In dreams those pertaining to sexual life are the
overwhelming majority...They represent the most primitive
ideas and interests imaginable." [2] In any case, in so far
as the instigating force behind every dream was an
unconscious wish--whether sexual or otherwise--it follows
from Freudian theory that every dream contains meaningful
messages in disguised form: the original wish or "dream
thought." The fact that all dreams contained unacceptable and
unpleasant wishes explained why dreams are so regularly and
so easily forgotten. This was because, reasoned Freud, they
were (deliberately) repressed: blacklisted by the ego and
sent by the censor to the bottom of the swamp of the
unconscious.

We know today, thanks to the last 30 years of dream research,
that dreams are not instigated by wishes or other
psychological forces, but by a periodic or automatic
biological process: REM sleep. If dreams are not triggered by
unconscious wishes, we can no longer assume that these wishes
play any role in dreams at all; and even worse for the
Freudian concept of meaning, we can no longer automatically
assume that every--or even any--dream has meaning! This is
not all of the news recent neuroscience has for Freud; but
let us save the bad news for the next section. The good news
for Freud is this: every period of dreaming sleep is
accompanied by sexual arousal, as indicated in males by
erections, and in females by increased vaginal blood flow.
Had Freud lived to hear of this phenomenon, he would have
almost certainly regarded it as a complete vindication of his
belief that at the bottom of every or almost every dream was--
sex!

The Activation-synthesis Model Of Dreaming

In 1977, Drs. Allan Hobson and Robert McCarley of Harvard
University presented a neurophysiological model of the dream
process that seriously challenged Freud's theory on virtually
every point. In a paper they published in the American
Journal of Psychiatry entitled "The Brain as a Dream State
Generator: An Activation-Synthesis Hypothesis of the Dream
Process," they suggested that the occurrence of dreaming
sleep is physiologically determined by a "dream state
generator" located in the brain stem. This brain stem system
periodically triggers the dream-state with such predictable
regularity that Hobson and McCarley were able to
mathematically model the process to a high degree of
accuracy. During the REM periods produced when the dream-
state generator is switched "on," sensory input and motor
out-put are blocked, and the forebrain (i.e., the cerebral
cortex, the most advanced structure in the human brain) is
activated and bombarded with partially random impulses
generating sensory information within the system. The
activated forebrain then synthesizes the dream out of the
internally generated information, trying its best to make
sense out of the nonsense it is being presented with."

"The primary motivating force for dreaming," emphasize Hobson
and McCarley, "is not psychological but physiological since
the time of occurrence and duration of dreaming sleep are
quite constant, suggesting a pre-programmed, neurally
determined genesis." They see the major drive for the
dreaming process as not only automatic and periodic but
apparently metabolically determined; of course, this
conception of the energetics of dreaming flatly contradicts
the classical Freudian notion of conflict as the driving
force for dreams.

As for the "specific stimuli for the dream imagery," they
continue, these appear to arise from the brain stem and not
from cognitive areas of the cerebral cortex. "These stimuli,
whose generation appears to depend upon a largely random or
reflex process, may provide spatially specific information
which can be used in constructing dream imagery." Hobson and
McCarley argue that the bizarre distortions in dream content
attributed by Freudians to the disguising of unacceptable
content by the "dreamwork" probably have a simpler
neurophysiological explanation instead: such bizarre features
of dreams as the condensation of two or more characters into
one, discontinuous scene shifts, and symbol formation may
merely directly reflect the state of the dreaming brain.

"In other words," the Harvard neurophysiologists argue, "the
forebrain may be making the best of a bad job in producing
even partially coherent dream imagery from the relatively
noisy signals sent up to it from the brain stem. The dream
process is thus seen as having its origin in sensorimotor
systems, with little or no primary ideational, volitional, or
emotional content. This concept is markedly different from
that of the 'dream thoughts' or wishes seen by Freud as the
primary stimulus for the dream."

Hobson and McCarley view "the elaboration of the brain stem
stimulus by the perceptual, conceptual, and emotional
structure of the forebrain," as primarily synthetic and
constructive, "rather than a distorting one as Freud
presumed." According to the Activation-Synthesis model, "best
fits to the relatively inchoate and incomplete data provided
by the primary stimuli are called up from memory...The brain,
in the dreaming sleep state, is thus likened to a computer
searching its addresses for key words. Rather than indicating
the need for disguise, this fitting of...experiential data to
[genetically programmed] stimuli is seen as the major basis
of the 'bizarre' formal qualities of dream mentation."
Scoring one more point against Sigmund Freud, they add that
"there is, therefore, no need to postulate either a censor or
an information degrading process working at the censor's
behest."

Hobson and McCarley see our usual poor ability to recall our
dreams as reflecting "a state-dependent amnesia, since a
carefully effected state change, to waking, may produce
abundant recall even of highly charged dream material." So
that if you are rapidly awakened out of REM sleep, you are
likely to remember dreams that you would otherwise be just as
likely to forget. Hammering a final nail into the coffin
containing Freud's theory of dreams, they write: "There is no
need to invoke repression to account for the forgetting of
dreams."

As was only to be expected, Hobson and McCarley's paper
stimulated counter attacks from the psycho-analytic
establishment, which responded that Freud's neurological
models were in no way crucial to his psychological theories.
In the view of Dr. Morton Reiser, Chairman of the Department
of Psychiatry at Yale University, and a past president of the
American Psychoanalytic Association,

McCarley and Hobson overextend the implications of their
work when they say it shows that dreams have no meaning. I
agree with them that their work refutes Freud's idea that a
dream is instigated by a disguised wish. Knowing what we do
now of brain physiology, we can no longer say that. The wish
may not cause the dream, but that does not mean that dreams
do not disguise wishes. The brain activity that causes dreams
offers a means whereby a conflicted wish can give rise to a
particular dream. In other words, wishes exploit--but do not
cause--dreams. [3]

The degree of controversy stimulated by the Hobson and
McCarley paper was truly remarkable. An Editorial in the
American Journal of Psychiatry a year later stated that the
Harvard paper "provoked more letters to the Editor than the
Journal had ever received before." Unexpectedly, what seemed
to be stirring so many people up was not Hobson and
McCarley's treatment of Freud, but their treatment of the
dream. The view that "dreams were after all merely the
senseless, random accompaniment of the autonomous electrical
activity of the sleeping Central Nervous System" did not sit
well with many dream researchers, to say nothing of
therapists and other dream workers accustomed to putting
dreams to a variety of practical uses.

Anybody who has ever awakened from a dream, exclaiming with
delight, "what a wonderful plot that was!" will know from
their own experience that at least sometimes, dreams are much
more coherent than would seem to be suggested by Hobson-
McCarley's model of "the forebrain making the best of a bad
job in producing even partially coherent dream imagery from
the...noisy signals sent up to it from the brain stem." In
the view of many scientists and dream researchers including
myself, the fact that dreams can be such superbly coherent
and entertaining stories is an indication of the need to
concede to the forebrain at least an occasional or partial
degree of control during dreaming. How could we construct
such extended and coherent dream plots if the higher brain
centers are limited to mere improvisation with whatever
unrelated props, people, and scenes that the "noisy signals"
from the brain stem happen to kick upstairs? The dream Hobson
and McCarley seem to envision would be like "And now for
something completely different!" every minute or two. The
fact that we are able at times to produce dreams that are so
wisely and elegantly constructed that they can and do serve
us as teaching stories suggests that higher order mental
functioning must in some way be able to influence the lower
order functioning of the dream state generator.

The phenomenon of lucid dreaming suggests even more strongly
the influence of the cerebral cortex on the construction of
dreams. For if your dreams were nothing more than the results
of your forebrain "making the best of a bad job in producing
even partially coherent dream imagery from the relatively
noisy signals sent up to it" from your brain stem, how would
you be able to exercise volitional choice in a lucid dream?
How would you be able to carry out a previously planned dream
action? How would you be able to deliberately decide to, let
us say, open a door to see what you might find there?

Lucid dream reports abound with counter examples, showing
that dreamers can at times have their own feelings,
intentions, and ideas. When dreamers realize that they are
dreaming, they often experience a feeling of exhilaration.
This feeling is more like a response to a higher order
perception, rather than to a random brain-stem stimulus. As
for intentions and ideas, when dreamers attain lucidity, they
typically remember intentions about what they wanted to do in
their next lucid dream, and can remember ideas in the form of
ideals and principles of behavior such as "face your fears,"
"seek positive outcomes," or "remember your mission." Our
oneironauts routinely make use of this last principle when
sleeping in the laboratory.

Finally, if all of the eye movements of REM sleep are
randomly generated by a madman in the brain stem, how are
lucid dreamers able to voluntarily execute eye movement
signals in accordance with pre-sleep agreement? Of course,
the answer to all of these rhetorical questions is that the
Hobson-McCarley hypothesis cannot be the whole story. On the
contrary, I believe Hobson and McCarley are right about much
of what they say about physiological determinants of the form
of dreams; it is evident that dreams also have psychological
determinants, and therefore any satisfactory theory of dream
content ought to include both. It also ought to explain why
and under what conditions dreams are sometimes coherent,
brilliantly witty narratives, and in other conditions,
incoherent ravings. And why in some dreams are we deluded and
in others lucid? And why are some dreams profoundly
meaningful and others pointless nonsense?

As for meaning and nonsense, the Activation-Synthesis model
of dreaming seems willing to completely disregard the
possibility that dreams could have any intrinsic or
interesting meaning whatever. Given the "forebrain making the
best of a bad job..." from the random signals sent up from
the brain stem, the most we could reasonably expect if this
were the case is what is called in computer terms "GIGO," an
acronym for "Garbage In, Garbage Out." Hobson, at least,
seems to say as much in a recent interview: "Dreams are like
a Rorschach inkblot. They are ambiguous stimuli which can be
interpreted any way a therapist is predisposed to. But their
meaning is in the eye of the beholder--not in the dream
itself." [4] I can hear it now: a psychiatrist asks a
patient, "What does this dream make you think of?" And
receives the reply: "An inkblot!"

Among the psychophysiologically minded dream researchers a
major criticism of the Activation-Synthesis model was that it
was essentially a one-way street, allowing traffic only to
proceed upward from brainstem to forebrain (from lower mental
function to higher mental function). But the way the brain is
actually put together would require a two-way street,
allowing forebrain control of brain stem activation, and
therefore allowing higher cortical functions such as thinking
and deliberate action to influence the dream. This is the
same criticism I just made regarding the inability of the
Hobson and McCarley model to deal with lucid dreaming.

Some sleep and dream researchers argued that the Activation-
Synthesis model missed the central question about dreaming
altogether. According to Dr. Milton Kramer of the University
of Cincinnati, Hobson and McCarley's approach is "not central
to the functional problems of dreaming. When it comes to
dreams, two things are important--meaning and function. Do
dreams enlighten us about ourselves? Will they make us
smarter, change our personality, change our mood, solve our
problems, have an application to our daily lives?" Kramer
concluded that "I think the essence of dreams is
psychological. It's all very well to find in dreams that a
person is walking. The important questions are, 'Where is he
walking? Why is he walking there?' Those are the continuing
mysteries of dreams and that is what we want to know." [5]

So how does the Activation-Synthesis model measure up if we
use Kramer's two criteria: meaning and function? As to the
meaning of dreams, in Hobson and McCarley's model there is
none. Regarding function, Hobson has offered a possible
function of the dream state:

A crude analogy to computers helps to make a point even if
it may violate the reality of brain function: Every
information processing machine has both hardware and software
components. To create a nervous system, the genetic code must
program both a structural blueprint and a set of operating
instructions. To maintain the neurons it would make sense to
utilize a standard set of operating instructions to activate
and test the system at regular intervals.
From an intuitive point of view, it is appealing to consider
REM sleep as the expression of a basic activity program for
the developing CNS that would ensure the functional
competence of neurons, circuits, and complex activity
patterns before the organism was called upon to use them. It
would be particularly important for such a system to have a
high degree of reliability in both time and in space. These
features are to be found in the periodicity and duration
constancy of REM and in the stereotyped nature of the
activity. [6]

Elsewhere, Hobson elaborates:

I believe that dreaming is the (sometimes outward) sign of
a genetically determined, functionally dynamic blueprint of
the brain designed to construct and to test the brain
circuits that underlie our behavior-including cognition and
meaning attribution. I also believe that this test program is
essential to normal brain-mind functioning but that you don't
have to remember its products to reap its benefits. [7]

Dreaming To Forget?

In a paper published in 1983 in the British journal Nature,
Nobel Laureate Francis Crick (one of the team that cracked
the genetic code and unraveled the mystery of DNA) and co-author
Graeme Mitchison proposed that the function of dream sleep

is to remove certain undesirable modes of interaction
in networks of cells in the cerebral cortex. We postulate
that this is done in REM sleep by a reverse learning
mechanism, so that the trace in the brain of the unconscious
dream is weakened, rather than strengthened by the dream. [8]

That, in a nut-shell, is their "reverse-learning" theory
of dreaming.

Crick and Mitchison's theory is derived from two basic
hypotheses: the first is that the cerebral cortex, as a
completely interconnected network of neurons, "is likely to
be subject to unwanted or 'parasitic' modes of behavior,
which arise as it is disturbed either by the growth of the
brain or by the modifications produced by experience."

Their second hypothesis is even more tenuous than the first:
it proposes that if these hypothetical 'parasitic' modes of
neuronal activity do in fact exist, then it might be that
they "are detected and suppressed by a special mechanism"
hypothetically operating during REM sleep. This mechanism is
described as having "the character of an active process which
is, loosely speaking, the opposite of learning." Crick and
Mitchison call this hypothetical process "reverse learning"
or "unlearning," and explain that it "is not the same as
normal forgetting" and that "Without it we believe that the
mammalian cortex could not perform so well."

"The mechanism we propose," write Crick and Mitchison,
drawing on the Hobson-McCarley conception of the
neurophysiology of dreaming,

is based on the more or less
random stimulation of the forebrain by the brain stem that
will tend to excite the inappropriate modes of brain
activity...especially those which are too prone to be set off
by random noise rather than by highly structured specific
signals. We further postulate a reverse learning mechanism
which will modify the cortex...in such a way that this
particular activity is less likely in the future...Put more
loosely, we suggest that in REM sleep we unlearn our
unconscious dreams. "We dream in order to forget."

To reiterate: what they are suggesting is that everything
that happens in any of your dreams is being actively
unlearned by your brain--that is why you are dreaming about
it: merely "in order to forget it."

What exactly does this mean? According to the reverse-
learning theory, when we remember our dreams we are re-
learning exactly what we were trying to unlearn. This would
seem to represent at least a partial failure of the reverse-
learning mechanism, and "one might wonder what effects its
failure might have." Crick and Mitchison suggest that
complete failure (remembering all of one's dreams) might lead
to "grave disturbances-a state of almost perpetual obsession
or spurious, hallucinatory associations..." A partial failure
(remembering several dreams a night) "should produce unwanted
responses to random noise, perhaps as hallucinations,
delusions, and obsessions, and produce a state not unlike
some schizophrenias."

Crick and Mitchison's motto is, "we dream in order to
forget." Well, maybe they do for all I know. Unfortunately,
they go further than that, seeming to feel that it would be
better for all of us to learn to forget our dreams: "In this
model," they write, "attempting to remember one's dreams
should perhaps not be encouraged, because such remembering
may help to retain patterns of thought which are better
forgotten. These are the very patterns the organism was
attempting to damp down."

Certainly, if the reverse learning model were followed to its
logical conclusion, it would seem to call for the shut-down
of all psychological analysis of dreams, all attempts at
remembering and interpretation of dreams, in fact the
complete shutdown of the dream work industry. Fortunately, it
appears that there is absolutely no direct evidence for
"unlearning" during REM. In fact, there doesn't appear to be
even any evidence for "unlearning" of any kind in any state,
in any living organism, anywhere. "Unlearning" as it now
exists is only a hypothetical concept, perhaps of some
relevance to computers, but there is no proof that it has any
application to human beings. In fact, Crick and Mitchison
admit "A direct test of our postulated reverse learning
mechanism seems extremely difficult." [9]

There is, in short, no convincing argument for this theory.
It just might be true or partially true, but until direct
evidence supporting it is brought forward, it must be viewed
as an unlikely possibility. Even if there were some substance
to reverse-learning theory, Crick and Mitchison's conclusions
about the desirability of dream recall are not necessarily
correct. On the contrary, the strongest argument against the
theory may be the catastrophic effects they predict to result
from even partial failure of the reverse-learning mechanism.
Certainly, people who habitually remember their dreams do not
seem any more prone to "hallucinations, delusions, and
obsessions" than are people who habitually forget their
dreams. Similarly, if the unlearning theory were true, dream
deprivation would interfere with the "reverse-learning"
process, producing disastrous effects. However, people have
been deprived of REM sleep for many nights and in some cases
years without showing any signs of mental breakdown. So for
any of you dreamers concerned about whether you may be
messing up your mind by remembering your dreams, I would
suggest that you need not worry!

The Functions Of Dreaming And The Advantages Of Consciousness

Let us return to the question with which we began this
chapter: "Why do we dream?" Though we have considered only a
few here, there are many answers that could be and have been
proposed to this question. But we can justly rule out in
advance any theory of the meaning and function of dreams that
does not make as much sense when applied to the dreams of a
tree shrew or a whale as to the dreams of a hairless speaking
primate--meaning us! Whatever the explanation for dreaming
must be, we must dream for the same reason that all mammals
have dreamed for more than a hundred million years. Then, why
do all mammals dream? Because all mammals have REM sleep.
Since humans are mammals, the biologically correct answer to
the question "Why do we dream?" is, "For the same reason that
any mammal does, because we have REM sleep." Yet, while
technically correct, this answer is not completely
satisfactory; for it merely leads to the question, "But then
why do all mammals have REM sleep?"

This is a question for evolutionary biology. According to the
available evidence, it seems that Active or REM sleep evolved
about one hundred and thirty million years ago, when early
mammals gave up laying eggs and first began to give birth
viviparously (born live, not hatched). Non-REM or Quiet
Sleep, on the other hand, seems to have arisen some fifty
million years earlier, when the warm-blooded mammals first
evolved from their cold-blooded reptilian ancestors.

The evolution of sleep and later of dreaming was far too
widespread and behaviorally significant to have occurred by
accident, and they presumably came into being through the
usual mechanism which Darwin made famous: "natural
selection". The idea is that just those genetic variations
which provide the organism with some survival advantage are
selected by evolution. Due to genetic variability, at any one
time there is a wide range of characteristics exhibited in
the population of every species. For any given environment,
some of these characteristics will be more favorable than
others to a species, increasing the probability that those
individuals of the species which possess the favorable
variation will live long enough to reproduce, passing on
their genes to progeny who in turn will be likely to survive
long enough to replicate, and so on. If an inherited trait
offers a large enough advantage, before long all members of a
given species will possess it, and carry the genes to pass it
on. Since this must have been the case with sleep and
dreaming, we can assume that they serve some adaptive (i.e.,
useful) function or functions.

All animals cycle once a day through a "circadian"
(approximately 24 hours long) rest-activity rhythm. Some
animals such as owls and mice rest in daylight and are active
at night; others, such as humans, usually act in the light
and rest in the dark. Sleep tends to occur during the rest
phase of the 24-hour cycles. Thus, one of the primary
adaptive advantages or "functions" of sleep is to enforce
immobility on the animal during the rest phase of the
circadian cycle, both to ensure its resting and keep it
safely in its nest, burrow, or home. Mother nature's original
idea of sleep (probably also familiar to your own mother) was
to keep you off the streets after dark, and out of trouble.

If you recall that NREM sleep arose at the same time that
mammals evolved from reptiles, you will have a hint as to an
additional function of sleep. Reptiles were dependent upon
external energy sources (primarily the sun) to maintain a
high enough body temperature to allow them to undertake the
business of living (principally feeding, fleeing and sex).
Although reptiles enjoy a lifelong free energy subsidy from
the sun, it wasn't always at their disposal, for example at
night, when they might have an urgent need to escape from
some hungry nocturnal predator. Warm-blooded mammals, on the
other hand, were no longer completely at the mercy of weather
and time of day, because they maintained their own constant
internal temperatures. The cost, however, was great: being
warm-blooded took much more energy than being cold-blooded.
Their inner fires had to be fueled with food that had to be
caught at no small energetic cost to the mammal. The need of
warm-blooded mammals to economize energy made energy
conservation therefore, an adaptive survival trait.
To see how effectively sleep accomplishes this function,
consider the case of two little mammals with high metabolic
rates, the shrew and the bat. The shrew sleeps very little
and has a life expectancy of no more than two years; the bat,
in contrast, sleeps twenty hours a day and as a result can
expect to live as many as eighteen years! If we convert these
lifetimes into years awake, the bat is still ahead with three
years of active life compared to the shrew's two. There seems
no doubt that sleep serves an energy conservation function
keeping warm-blooded, fast-moving creatures from burning out
too fast. This suggests that there is more truth than fiction
to the old aphorism about getting a good night's sleep!

All right, you might say, so that's why we have Quiet Sleep,
but why did Active Sleep evolve and with it dreaming?
Certainly, there must have been very good reasons for it,
since this state has many disadvantages. For one, your brain
uses much more energy during dreaming than it does while
awake or in Quiet Sleep. For another, there is the fact that
the body is paralyzed while you are dreaming, significantly
increasing the sleeper's vulnerability. In fact, the amount
of dreaming sleep for a given species is directly
proportional to the degree of safety from predators; the more
dangerous life is, the less a species can afford to dream.

Given these drawbacks, Active Sleep must have offered
particularly useful advantages to the mammals of one hundred
and thirty million years ago. We can guess one advantage if
we remember that this was just the point in evolutionary
history when mammalian mothers gave up laying eggs in favor
of bearing live young instead. So what advantages might
Active Sleep have offered to our ancestral mothers? The
answer can be seen, I think, if you recall that egg-hatched
lizards or birds break out of their own shells already
sufficiently developed to survive on their own if necessary.
Viviparous offspring, of which the human baby provides an
unexcelled example, are, on the contrary, less developed at
birth and often completely, helpless. Viviparous infants have
to get through a great deal of learning and development,
especially of the brain, in the first few weeks, months, and
years of life.

In contrast to the hour and a half an adult spends in REM
sleep each night, a new-born baby, who sleeps sixteen to
eighteen hours a day is likely to spend 50% of all this time--
as much as nine hours a day--dreaming! The fact that the
amount and proportion of REM sleep decreases throughout life
suggested to several dream researchers [10] that REM sleep
may play an important role in the development of the infant
brain, providing an internal source of intense stimulation
which would facilitate the maturation of the infant's nervous
system as well as help in preparing the child for the
limitless world of stimulation it will soon have to face.

The foremost French sleep researcher, Professor Michel
Jouvet, of the University of Lyon, has proposed a similar
function for Active Sleep: according to him, dreaming permits
the testing and practicing of genetically programmed (i.e.,
instinctual) behaviors without the consequences of overt
motor responses--thanks to the paralysis of this Paradoxical
state of sleep. So the next time you see a newborn baby girl
or boy smiling in their sleep, don't be surprised if they
turn out to be perfecting their perfect smile to charm a
heart they are yet to meet!

Well then, so now we know why babies dream. But if that were
all there is to it, why wouldn't REM sleep completely
disappear by adulthood? Well it might, except that there does
seem to be something more to it, providing adults with a good
reason to continue to dream. The reason is this: Active Sleep
has indeed been found to be intimately involved with learning
and memory.

The evidence connecting the dream state with learning and
memory is of two kinds: the most direct evidence is an
extensive body of research indicating that learning tasks
that require significant concentration or the acquisition of
unfamiliar skills is followed by increased REM sleep. The
second type of evidence is less direct but still quite
convincing: many studies have shown that memory for certain
types of learning is impaired by subsequent REM deprivation.
Psychologists distinguish two varieties of learning:
prepared and unprepared learning. Prepared learning is
easy and quickly acquired while unprepared learning is
difficult and only slowly mastered with great effort.
According to Boston psychiatrists Dr. Ramon Greenberg and Dr.
Chester Pearlman, it is only unprepared learning that is REM-
dependent. In of their experiments, which involved rats, they
easily learned that cheese was located behind one of two
doors--and an electric shock behind the other: this is called
"simple position" learning, and most animals are well
equipped for it. If on the other hand, the position of reward
and punishment are reversed on successive trials, so that
each time shock is to be found where cheese was on the
previous trial and vice versa, most animals find it difficult
(or impossible) to work out this more complex pattern and
learn where to expect what; in other words, for rats,
"successive position reversal" is an instance of unprepared
learning.

After Greenberg and Pearlman subjected rats to these two
varieties of task, they deprived them of REM sleep and then
re-tested the rats for learning. They reported that while
simple position learning was unimpaired by REM deprivation,
successive position reversal was "markedly" impaired. "This
finding is noteworthy" they remarked, "because successive
position reversal is a task which clearly distinguishes the
learning capacities of species with REM sleep (mammals) from
those without it (fish)." The implication is that REM sleep
makes more complex learning possible than would otherwise be
the case.

Greenberg and Pearlman conclude that dreaming sleep "appears
in species that show increasing abilities to assimilate
unusual information into the nervous system." They suggest
that the evolutionary development of the dream state "has
made possible the increasingly flexible use of information in
the mammalian family. That this process occurs during sleep
seems to fit with current thinking about programming and
reprogramming of information processing systems. Thus,
several authors have pointed out the advantage of a separate
mechanism for reprogramming the brain in order to avoid
interference with ongoing functions." [11]

One of these authors is Christopher Evans, whose computer-
analogy theory of dreams is presented in his recent book,
Landscapes of the Night: How and Why We Dream. The late Dr.
Evans was an English psychologist with an abiding interest in
computers who proposed that dreaming is the brain-computer's
"off-line" time when the mind is assimilating the experiences
of the day and at the same time updating its programs.

Not only is dreaming associated with learning and memory, but
it also appears to play a somewhat broader role in the
processing of information in the nervous system, including
coping with traumatic experiences and emotional adjustment.
The dream state has also been proposed as a restorative for
mental functioning; according to Professor Ernest Hartmann,
REM sleep helps us to adapt to our environments by improving
our mood, memory, and other cognitive functioning through
restoring certain neurochemicals that are depleted in the
course of waking mental activity. [12]

Dreaming sleep has also been shown to play a general role in
reducing brain excitability. [13] It can have a favorable
effect on our moods, making us, for example, less irritable.
Janet Dallet, in a dissertation, has reviewed a number of
theories of dream function, concluding that "contemporary
theories tend to focus on the function of environmental
mastery, viewed from one of three perspectives: (a) problem
solving (b) information processing, or (c) ego
consolidation." [14]

In dreams we witness something more
than mere wishes; we experience dramas reflecting our
psychological state and the process of change taking place in
it. Dreams are a laboratory for experimenting with changes in
our psychic life...This constructive or synthetic approach to
dreams can be clearly stated: Dreaming is an endogenous
process of psychological growth, change and transformation. [15]

It might be said of the diverse theories of dream function
that they all are partly right and they all are partly wrong:
right in so far as they say what a function of dreaming is,
and wrong to the extent that they say what the function of
dreaming is. The situation is analogous to the traditional
tale of the blind men and the elephant. In this story the
blind men each sought to discover the nature of an elephant
by means of touch alone. From the part they grasped, they
believed they knew the nature of the whole. An elephant was
like a rope for the blind man who grasped it by the tail;
like a rug for the one who grasped its ear; like a pillar for
the one who grasped its leg; and so on. In like manner, the
proponents of the various theories of dreams have each
grasped not the whole as they thought, but a part of the
function of dreams. Freud, for example, in surveying the many
opinions about dreams, judged almost all of these previous
views to have missed the forest for the trees. His own
theory, which placed great importance on sex as the basis of
all dream content, he considered a "view from the heights,"
but--as it is perhaps apparent today--Freud himself mistook a
wood for the world. And as the irreverent have put it, he
seems to have grasped the elephant by the balls. Things could
be worse though, for others seem to have grasped the elephant
by "the feathers"!

Putting aside, for the moment, the question of the special
functions of dreaming, let us ask what is the most basic or
general function that dreaming is likely to serve. Since
dreaming is an activity of the brain, we must first ask what
function brain activity serves? And because the most general
biological purpose of living organisms is survival, this must
also be the most general biological answer to the purpose of
brain activity. The brain fosters survival by regulating the
organism's transactions with the world and with itself. These
latter transactions would perhaps be best achieved in the
dream state, when sensory information from the external world
is at its minimum.

As organisms proceed up the evolutionary ladder, new forms of
cognition and corresponding actions emerge. The four major
varieties of action are reflexive, instinctive, habitual and
intentional, in ascending order. Behaviors lower on the
evolutionary scale are relatively fixed and automatic, while
behaviors higher on the scale are more flexible. Automatic
behaviors are best if the situation they are designed for is
relatively invariable. So, for example, since we must breathe
every minute of our lives, this is very efficiently
accomplished by a reflexive mechanism. Likewise, instinctive
action is effective as long as the environment we are in is
not too different from the one our ancestors lived in. Habit,
too, is useful while the environment we have learned to get
along in doesn't change too much. Intentional or deliberate
action has evolved in order to handle environmental changes
("novelty") that our habitual behavior is inadequate to cope
with. This highest level of cognition, which allows
intentional action, is usually referred to as reflective
consciousness. It is the same cognitive function that we call
lucidity, when speaking in the context of dreaming.

Reflective consciousness offers the advantage of flexible and
creative action as much to the dream state as to the waking
state. More specifically, consciousness allows dreamers to
detach themselves from the situation they are in, and reflect
on possible alternative modes of action. Lucid dreamers are
thus able to act reflectively, instead of merely reflexively.
The important thing for lucid dreamers is their freedom from
the compulsion of habit; they are capable of deliberate
action in accordance with their ideals, and are well able to
respond creatively to the dream content. Seen in this light,
lucid dreaming does not at all appear as a mere abnormality
or meaningless curiosity; rather, it represents a highly
adaptive function, the most advanced product of millions of
years of biological evolution.

The Meaning Of Dreaming

Since the evidence indicates that dreaming serves important
biological functions, dreaming cannot be "meaningless
biology." On the contrary, dreams are, at very least,
meaningful biology. But does this mean that dreams must be
meaningful psychology? I think the answer is "not
necessarily." If you ask, "What do dreams mean?" the answer
will depend upon just exactly what you mean by "meaning." But
perhaps we can agree to use "meaning" to mean placing
anything--let us say, in this case, a dream--in some
explanatory context or other. Please note, however, that
explanatory contexts vary widely from person to person. For
some, interpretation or translation seems most appropriate
under the assumption that dreams are messages to ourselves.
Others will seek mechanistic explanations in a physiological
or psychological context, and still others will be inclined
to treat the dream on its own terms as it relates to itself.
Which approach is right? Or, rather, which is right for which
dream?

Freud assumed that the events occurring in dreams (lucid or
otherwise) were by their very nature necessarily symbolic of
unconscious motives. This assumption, although undoubtedly
correct in certain circumstances, is equally undoubtedly
misleading in others. Many dream interpreters would like to
believe that every element of every dream is equally subject
to symbolic interpretation, or that "all dreams are equal."
This is an understandable belief, for dream interpreters
could not expect to stay in business for very long if they
were to say of a dream presented for analysis that "this
dream is meaningless," or even, "not very interesting."
Dreamers meeting with such responses would be inclined to
take their dreams elsewhere until they found someone more
willing to tell them what their dreams "really" meant. Also,
it is a sensible working hypothesis when presented with a
dream for interpretation to assume that the dream does have
meaning, or, at least, that part of it does.

In the case of psychotherapists and their clients, the
relevant kind of meaning assumed and sought is psychological.
However, the assumption that every dream contains significant
psychological information is yet to be subjected to rigorous
test. It seems to me that to assert that every dream is
equally informative psychologically or otherwise, informative
is like supposing that every sentence you say is equally
interesting, coherent, or profound!

There is a contrary way of looking at dreams, the
"existential" view, which treats dreams as lived experiences
composed of imagined interactions and elements which could be
symbolic, or literal, or somewhere in between. Flying, for
instance, could be in one case the symbolic expression of any
number of unconscious desires, such as the wish to transcend
all limitation, or as Freud would suggest, the wish to engage
in sexual activity. While in another case, it might be merely
the most convenient mode of travel available to the dreamer
who wants to move from one place to another within the dream
world.

From these foregoing considerations, we would probably be
wiser to leave the degree of symbolic significance attributed
to a given dream event as an empirical rather than an
axiomatic matter--as something to test rather than to assume.
It seems safe to conclude that for a given dreamer and dream,
flying was apparently symbolic of this or that for a certain
dreamer and dream only if such an interpretation either
impresses the dreamer as having a sufficiently significant
explanatory power for his dream, or if it is otherwise
supported by compelling evidence.

It is important to realize that just because a particular
dream can sometimes be interpreted in symbolic terms doesn't
mean that it was intended as a communication in the first
place. If dreams are important messages to ourselves, as
suggested by the oft-repeated proverb--"an uninterpreted
dream is like an unopened letter", then why do we throw most
of them away? This is surely what we do when we forget our
dreams and we forget the great majority of them. The "letter-
to-yourself" theory of dreams is in even worse trouble when
we remember the mammalian origins of dreaming. Consider the
family dog: of the tens of thousands of dreams that Fido will
dream in his lifetime--how many are likely to be interpreted?
By Fido, none at all! By his owners, perhaps a few. But if
humans are the only mammals equipped with the linguistic
skills to use symbolic language, what purpose could dreaming
serve for the thousands of species of non-human dreamers? And
if it could serve no purpose to our ancestors, how could it
have ever evolved?

I think that the answer is clear. Dreaming must serve
purposes other than talking-to-ourselves, as I spoke of
earlier in the chapter; moreover, these purposes must be
achievable without requiring dreams to be remembered, to say
nothing of interpreted. In fact, there is a good reason why
remembering dreams might be maladaptive for all non-
linguistic species, including our ancestors. To see why,
consider how we are able to distinguish memories of events
that we dreamed and those that actually occurred. It is
something that we have learned to do thanks to language.
Remember Piaget's account of the child's development of the
concept dream. When, as children, we remembered our
earliest dreams, we assumed, at first, that they had
"actually" happened just like everything else. After enough
repetitions of our parents telling us that some of our
experiences were "only dreams" we learned to distinguish
memories of inner dream events from memories of external
physical world events. But how would we ever have been able
to untangle the two realities without the help of other
people telling us which was which?

Animals, however, have no way to tell each other how to
distinguish dreams from reality. Imagine your favorite cat
living on the other side of a tall fence that protects it
from a vicious dog. Suppose your cat were to dream that the
wicked dog was dead, and replaced by a family of mice. What
would happen if the cat were to remember this dream when it
awoke? Not knowing it was a dream, it would probably hungrily
jump over the fence, expecting to find a meal. But instead,
it would find itself a meal--for the dog!

Thus dream recall would seem to be a bad thing for cats,
dogs, and all of the rest of the mammalian dreamers except
humans. This could explain why dreams are difficult to
recall. They may be so, according to this view, because of
natural selection. We and our ancestors might have been
protected from dangerous confusion by the evolution of
mechanisms that made forgetting dreams the normal course of
affairs. But if the theory I have proposed for why dreams are
difficult to recall is correct, contrary to Crick and
Mitchison, remembering dreams should do humans no harm,
precisely because they can tell the difference between dreams
and waking experiences.

In conclusion, I would suggest that the dream is not so much
a communication as a creation. In essence, dreaming is more
like world making than like letter writing. And if, as we
have seen, an uninterpreted dream isn't like an unopened
letter, then what is it like? Having demolished a popular
proverb, let us replace it with another, that seems to come
closer to doing the dream justice: "an uninterpreted dream is
like an uninterpreted poem". If I am right, dreams have much
more in common with poems than they do with letters. The word
poem is derived from a Greek very meaning to create, and I
have already argued that the essence of dreaming is closer to
creation than to communication. Are all poems equally worth
interpreting? Are all poems equally coherent, effective, or
worth reading? If you wrote a dozen poems a night every night
of your life, what do you suppose you would find among your
several hundred thousand poems. All masterpieces? Not likely.
All trash? Not likely either. What you would expect is that
among great piles of trivial doggerel, there would be a
smaller pile of excellent poems, but no more than a handful
or perfect masterpieces. It is the same with your drams, I
believe. When you have to do five or six shows every night,
many of them are likely to lack inspiration. It is true that
you can cultivate your dream life so that the time you spend
there will grow more rewarding as the years pass. But why
should you expect that every one of your dreams is worth
taking the time to interpret? And yet, if a poem or a dream
calls out to you to interpret it, by all means find out what
it means.

It would be a very unusual poet who created poetry primarily
for the amusement and instruction of critics or interpreters.
He or she doesn't need a critic on hand in order to be
affected, perhaps even transformed, by the poem's creation.
When we read a poem, we don't need to interpret it to be
deeply moved, edified, inspired, and perhaps even
enlightened. Having said that neither poems nor dreams have
any need of interpretation doesn't mean that it is never
useful. On the contrary, it seems clear that intelligent
criticism or interpretation can at times greatly increase the
depth of our understanding of a poem and in the best of
circumstances, of ourselves as well. It is the same with the
dream.

Notes

[1] Hobson, J.A. & McCarley, R.W. The brain as a dream-state
generator: An activation-synthesis hypothesis of the dream
process. AMERICAN JOURNAL OF PSYCHIATRY, 134:1335-1348, 1977.